Our research interests are broad, but focus on Quaternary landscape dynamics and paleoenvironmental reconstruction. We use a variety of research methods, tools, and techniques to investigate the spatiotemporal variability of landscape-scale vegetation dynamics (those influenced by people or natural processes). We address questions that require the integration of present-day climatic and ecological processes with those that functioned in the past and those that are likely to become altered in the near-future due to human-induced changes.
Shipwreck rates reveal Caribbean tropical cyclone response to past radiative forcing
Read about the project in the journal Proceedings of the National Academy of Sciences of the United States of America: http://www.pnas.org/content/early/2016/03/02/1519566113
- Twenty-first-century North Atlantic tropical cyclone (TC) projections are crucial for the development of adaptation and mitigation strategies, but they are subject to large uncertainties, particularly with respect to TC response to radiative forcing.
- We used a combination of tree-ring data and historical shipwreck data to show that TC activity in the Caribbean was distinctly suppressed during the Maunder Minimum (1645–1715 CE), a period when solar irradiance was severely reduced.
- This solar fingerprint on decadal-scale Caribbean TC variability implies modulation by a combination of basin-wide climatic phenomena.
- Our findings highlight the need to enhance our understanding of the response of atmospheric circulation patterns to radiative forcing and climate change to improve the skill of future TC projections.
Read about the project in the journal Proceedings of the National Academy of Sciences of the United States of America: http://www.pnas.org/content/early/2016/03/02/1519566113
Suwannee River flow variability 1550–2005 CE reconstructed from a multispecies tree-ring network
· Streamflow is reconstructed for the Suwannee River, Florida during the period 1550–2005 CE
· Instrumental flow does not capture the full range of variability over past 455 years
· Future planning based on the current flow regime could be problematic for natural and human systems
· Streamflow is reconstructed for the Suwannee River, Florida during the period 1550–2005 CE
· Instrumental flow does not capture the full range of variability over past 455 years
· Future planning based on the current flow regime could be problematic for natural and human systems
Dendroclimatic reconstructions using multiple co-occurring tree species
Co-PI: Justin Maxwell (Indiana University)
We investigate the ability of using multiple co-occurring canopy-dominant species from a single location for climate reconstructions based in the eastern United States (US). The composite chronology reconstruction outperforms each individual species model, indicating that using multiple co-occurring species increases reconstruction skill, at least from a single study site in Indiana. Furthermore, model performance is improved by using nested reconstruction techniques, and implicates the potential ability to use multiple co-occurring species across multiple locations in the eastern US.
Co-PI: Justin Maxwell (Indiana University)
We investigate the ability of using multiple co-occurring canopy-dominant species from a single location for climate reconstructions based in the eastern United States (US). The composite chronology reconstruction outperforms each individual species model, indicating that using multiple co-occurring species increases reconstruction skill, at least from a single study site in Indiana. Furthermore, model performance is improved by using nested reconstruction techniques, and implicates the potential ability to use multiple co-occurring species across multiple locations in the eastern US.
Fire synchrony and the influence of Pacific climate variability on wildfires in the Florida Keys, USA
Co-PIs: Henri D. Grissino-Mayer, Sally P. Horn (University of Tennessee)
We compared crossdated fire-scar chronologies from two islands in the lower Florida Keys, Big Pine Key (BPK) and No Name Key (NNK), to measured values of the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), El Niño-Southern Oscillation (NIÑO3.4), Pacific Decadal Oscillation (PDO), Interdecadal Pacific Oscillation (IPO), and divisional temperature and precipitation over the period 1856–1956. Large-scale climate anomalies captured by ENSO (NIÑO3.4) and IPO indices had combined effects on widespread fires. Superposed epoch analysis revealed that widespread fires on BPK occurred during years that were drier than average, and when constructive phases (years of combined warm [positive] or cool [negative] phases) of ENSO and the IPO occurred 3 years and 1 year prior to fires. Positive phases of the PDO were also significantly associated with widespread fires 3 years prior to events, but the PDO was not influential 1 year prior to fires. While fire years were temporally synchronous between the two islands during the period 1818–1924 (n = 10), we did not find significant relationships between climate and fire on the smaller NNK, which suggests that island size influences the ability to detect broad-scale climate forcing of wildfires in the Florida Keys.
We compared crossdated fire-scar chronologies from two islands in the lower Florida Keys, Big Pine Key (BPK) and No Name Key (NNK), to measured values of the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), El Niño-Southern Oscillation (NIÑO3.4), Pacific Decadal Oscillation (PDO), Interdecadal Pacific Oscillation (IPO), and divisional temperature and precipitation over the period 1856–1956. Large-scale climate anomalies captured by ENSO (NIÑO3.4) and IPO indices had combined effects on widespread fires. Superposed epoch analysis revealed that widespread fires on BPK occurred during years that were drier than average, and when constructive phases (years of combined warm [positive] or cool [negative] phases) of ENSO and the IPO occurred 3 years and 1 year prior to fires. Positive phases of the PDO were also significantly associated with widespread fires 3 years prior to events, but the PDO was not influential 1 year prior to fires. While fire years were temporally synchronous between the two islands during the period 1818–1924 (n = 10), we did not find significant relationships between climate and fire on the smaller NNK, which suggests that island size influences the ability to detect broad-scale climate forcing of wildfires in the Florida Keys.
Paleo-perspectives of fire and vegetation change inferred from bog sediments, De Soto Ranger District, Mississippi
Funded by U.S. FOREST SERVICE
Co-PI: Andy Reese, Frank Heitmuller (University of Southern Mississippi)
Little is known about wildfire activity in bogs located in the Southeast United States. Charcoal preserved in sediments provides a record of past fire occurrence. By analyzing abundances of macroscopic (typically > 100 microns in length) charcoal, pollen assemblages, and organic matter within sediments, we aim to provide an assessment of the wildfire activity and document changes in vegetation regimes throughout the history of the bog.
Co-PI: Andy Reese, Frank Heitmuller (University of Southern Mississippi)
Little is known about wildfire activity in bogs located in the Southeast United States. Charcoal preserved in sediments provides a record of past fire occurrence. By analyzing abundances of macroscopic (typically > 100 microns in length) charcoal, pollen assemblages, and organic matter within sediments, we aim to provide an assessment of the wildfire activity and document changes in vegetation regimes throughout the history of the bog.
Underwater cypress forest, northern Gulf of Mexico
Funded by BUREAU OF OCEAN ENERGY MANAGEMENT, THE WALLACE RESEARCH FOUNDATION, USM CENTER FOR UNDERGRADUATE RESEARCH
Co-PIs: Kristine DeLong (Louisiana State University), Kenneth Barbour (University of Southern Mississippi), Ben Raines (Weeks Bay Foundation)
Tropical cyclones in the Northern Gulf of Mexico between 2004 and 2008 uncovered an ancient forest of previously buried logs and tree stumps in growth positions located off the coast of Mobile, Alabama. Personal observations during diving expeditions and surveys with multi-beam and side-scan sonar revealed more than 50 in-situ, well-preserved stumps and logs. Given the scarcity of annual climate records during this time and in this geographic region, and the wealth of scientific potential that exists at the site, collecting tree-ring and sediment records at the site is imperative given that (1) the samples are no longer in an anoxic environment and decomposition by marine organisms has started; and (2) the site will likely experience secondary burial during the next Gulf Coast tropical storm. These unique tree-ring and sediment records will provide a better understanding of climate change that will be coupled with the geomorphological and biogeographical response of this iconic tree species during the glacial period along the Gulf Coast region.
Co-PIs: Kristine DeLong (Louisiana State University), Kenneth Barbour (University of Southern Mississippi), Ben Raines (Weeks Bay Foundation)
Tropical cyclones in the Northern Gulf of Mexico between 2004 and 2008 uncovered an ancient forest of previously buried logs and tree stumps in growth positions located off the coast of Mobile, Alabama. Personal observations during diving expeditions and surveys with multi-beam and side-scan sonar revealed more than 50 in-situ, well-preserved stumps and logs. Given the scarcity of annual climate records during this time and in this geographic region, and the wealth of scientific potential that exists at the site, collecting tree-ring and sediment records at the site is imperative given that (1) the samples are no longer in an anoxic environment and decomposition by marine organisms has started; and (2) the site will likely experience secondary burial during the next Gulf Coast tropical storm. These unique tree-ring and sediment records will provide a better understanding of climate change that will be coupled with the geomorphological and biogeographical response of this iconic tree species during the glacial period along the Gulf Coast region.